Human cytomegalovirus is an opportunistic pathogen that produces a devastating central nervous system disease in AIDS patients and is the most common infectious cause of congenital brain disorders. Though the importance of lymphocytes in clearing viral brain infection is well appreciated, recent data have suggested that infiltrating T lymphocytes may also play an integral role in repair of brain tissue damaged during viral infection. In this proposal, the central hypothesis to be tested is that cytomegalovirus infection of neural stem cells (NSCs) compromises their neuroreparative response to T lymphocyte-mediated clearance of viral brain infection. The proposed experiments are designed to study the effect of murine cytomegalovirus (MCMV) infection on the interplay between T-cells and NSCs in vivo. To test this hypothesis, we will (1) determine if NSCs respond to T lymphocyte-mediated viral clearance. This will be achieved by depleting CD8+, CD4+, and Treg (CD4+CD25+) lymphocyte subpopulations and examining the subsequent effect on NSC migration to sites of MCMV brain infection using real-time bio-luminescence imaging. We will also investigate how T-cell-mediated immune responses affect the production of select neurotrophins in the brains of infected animals. We will then (2) determine if MCMV infects endogenous NSCs in vivo and compromises their response to T lymphocytes. These studies will examine the effect of MCMV infection on the migration of luciferase-labeled NSCs towards IFNg3-induced chemokine production and determine if MCMV infected NSCs are themselves targets for CD8+ T-cell-mediated clearance. Finally, we will (3) determine if viral infection of NSCs alters their subsequent neurogenesis. These studies will investigate persistence of transplanted luciferase-labeled NSCs and evaluate how MCMV infection alters which neural cell markers (specific for neurons, oligodendrocytes, or astrocytes) are expressed following subsequent differentiation in vivo. In the final studies, we will determine if an anti-inflammatory environment fosters regenerative processes through overexpression of interleukin (IL)-10 and transforming growth factor (TGF)b2, followed by an assessment of neurogenesis. Taken together, the studies proposed in this competitive renewal application will provide new insights into the interactions between T lymphocytes and NSCs in the maintenance of healthy brain tissue following viral infection. PUBLIC HEALTH RELEVANCE Human cytomegalovirus is an opportunistic pathogen that produces a devastating central nervous system disease in AIDS patients and the murine models described in this grant application will help us to understand interactions between antiviral immune responses and brain repair. The prognosis for full recovery in patients suffering from chronic disability following viral encephalitis is poor and the experiments outlined in this proposal are timely because the use of neural stem cells to repair brain damage is currently being explored in numerous models of neurodegenerative diseases. Because it is believed that one function of neural stem cells is to repair inflamed and damaged brain tissue, these cells may offer an innovative approach to treat the neuropathological sequelae subsequent to neuroAIDS, as well as other viral encephalitis.